Tractors are known which comprise a continuously variable transmission (CVT) for transmitting a torque from an internal combustion engine to a driving axle and hence to the wheels. Known continuously variable transmissions may comprise a hydrostatic transmission including a hydrostatic unit. The latter in turn comprises a variable displacement hydraulic pump connected to a hydraulic motor. By varying the displacement volume of the hydraulic pump, the torque applied to the wheels can be set to the desired value. A control device, comprising for example an electro-valve, is provided for controlling the hydraulic unit. It may happen that, during life of a tractor, the hydraulic transmission does not work properly. In this case, it is not easy to understand which component of the hydrostatic transmission causes the problem. In other words, it is not easy to understand whether there is a fault either in the hydrostatic unit, or in the electro-valve, or in any other component.
Therefore, in order to quickly repair the tractor, the whole hydrostatic unit is often removed and replaced by a new hydrostatic unit. This is a very expensive way of obviating the fault, especially if it is later discovered that the removed hydrostatic unit was actually working properly and that the malfunctioning was due to another component.
An object of the invention is to improve known vehicles, particularly working vehicles such as wheeled or crawler tractors and excavators.
Another object is to avoid removing a hydrostatic unit from the vehicle in a case in which the hydrostatic unit is actually working properly.
A further object is to minimize costs and time required by maintenance and repairing operations of a vehicle.